This invention relates to a screen for a carding machine. The screen which extends generally underneath the carding cylinder, has a central part and two end parts. One of the end parts projects into the zone between the lickerin and the carding cylinder. An additional screen is arranged underneath the lickerin.
In practice the screen extending underneath the carding cylinder is made of several sections for manufacturing reasons. The central part of the screen is provided with screen bars, while the two end parts are free from such screen bars. The known screen of the above-outlined type has, in essence, three functions: it separates waste, it equalizes excess air pressure and it guides the fibers. In the known arrangement, underneath the carding cylinder two cylinder screen parts adjoin the lickerin screen which projects into the corner zone between the lickerin and the carding cylinder. The cylinder screen part which joins the lickerin screen as well as the cylinder screen half which is situated in the vicinity of the doffer are provided with closed sheet metal portions corresponding to a screen length having about 20 screen bars. Between these screen parts there are situated the screen bars which are spaced from one another at a distance which corresponds to one-half of one bar width. Such a known screen structure, as noted above, serves for guiding the fibers and for simultaneously regulating the pressure of the entrained air as well as for separating the waste as well as fiber fragments or short fibers no longer used in the successive steps of the spinning process.
It is a disadvantage of card screens of the above-outlined type that they do not process satisfactorily short fibers because the latter are caught in the clearance between the screen bars and form a packed, chunky mass. As carding operation is started, the screen clothing tears these chunks away and squeezes them into the clearance between the clothing of the carding cylinder and the screen, resulting in a damage to the cylinder screen. Also, the risks are high that the entrained fiber chunks press the lickerin screen against the lickerin clothing.